Hydraulic backup rolls for rotary veneer lathe



March 12, 1968 H. E. JAMES ETAL 3,372,721

HYDRAULIC BACKUP ROLLS FOR ROTARY VENEER LATHE Filed April l, 1966 2 Sheets-Sheet l I NVEN T0125 ATMP/QE@ March 12, 1968 H; E. JAMES ETAL. 3,372,721

HYDRAULIC BACKUP ROLLS FOR ROTARY VENEER LATHE Filed'April 1, 1966 2 Sheets-Sheet 2 /0' 2 INVENTORS #0h/4,@ E. JAMES' JA CK A 55mm/SKV United States Patent tice 3,372,721 Patented Mar. 12, 1968 3,372,721 HYDRAULIC BACKUP RLLS FOR ROTARY VENEER LATHE Howard E. .lames and Jack A. Schikofsky, Marie, Ontario, Canada, assignors to Weycrhaeuser Company, Tacoma,

ash., a corporation of Washington Filed Apr. 1, 1966, Ser. No. 539,484 7 Claims. (Cl. P14- 209) The invention relates to an apparatus for stabilizing logs in a rotary veneer lathe. More specifically, this invention relates to backup rolls that resist the forces which tend to distort a log being cut in a rotary veneer lathe.

In a rotary veneer lathe, a log is chucked between rotatable and axially adjustable spindles. Dogs having protruding spurs are attached to each spindle end and imbed themselves into the end of the leg, thus providing means for transmitting the torque of the rotating spindles to the log. In a conventional rotary veneer lathe, the log is rotated against a knife which is attached to a knife carriage. The carriage is mounted on any suitable means and is fed toward the log at a controlled rate per revolution of the log. The carriage is usually provided with a pressure cap unit carrying a locally adjustable abutment bar that is set parallel to the knifes edge both in a horizontal and a vertical plane. Thus, the edges of the knife and the bar form the boundaries of a slot of uniform cross section whose width is set at a distance slightly less than the thickness of the veneer being cut. The pressure of the abutment bar against the log is applied slightly above the knifes edge at a point which will cause a minimum of splitting action by the wedge shaped knife and causes the knife to actually cut the compressed bers as the ribbon of veneer is severed from the rotating log, The ribbon of veneer is in effect extruded through the slot formed by the edges of the knife and the abutment bar which is well known to those skilled in the art.

When cutting rotary veneer, there is a reaction to the force required to rotate the log. Its major component is roughly upwards. There is also a reaction to the force required to feed the knife into the log combined with the pressure of the abutment bar against the log. This component of the force is roughly horizontal. The magnitude of 4the above forces depends upon numerous factors such as thickness of veneer being cut, density of the wood, pressure applied by the abutment bar and sharpness of the knife edge. Thus, the forces may vary over a wide range. Without suitable backup rolls, these forces can only be resisted by the stillness of the log acting as a beam. Depending upon the conditions that exist, a log being cut in a nominal 8 lathe will start to noticeably deect when reduced to a diameter of about 13 to 8". To cut acceptable quality veneer having a minimum of internal stresses, one of the necessary requirements is that the ribbon of veneer be cut from a true cylinder. When a log begins to deect longitudinally due to the above-mentioned forces, the length of the diameter at the ends becomes less than the length of the diameter at the center. The ribbon of veneer being cut then becomes longer along its edges than along its longitudinal center line, resulting in the formation of a noticeable buckle which is objectionable.

Accordingly, the major function of backup rolls is to resist the longitudinal deflection of the log so that the ribbon of veneer will be cut from a true cylinder from its maximum diameter down to the minimum diameter core. Since the distance of the knife to the center is controlled through feeding of the lathe carriage knife which has been previously set for the thickness of veneer being cut, it follows that in a successful backup roll arrangement, the same feed means must cause each backup roll to individually feed toward the center of rotation at the same rate as does the knife. This condition can be met by mounting each backup roll independently of the other and so positioned that each roll moves in a true radial line through the spindle center of the lathe which, in effect, is the center of the log rotation.

An object of this invention is to provide backup rolls for stabilizing logs in a rotary veneer lathe.

Another object of this invention is to provide backup rolls that resist the forces which tend to distort the log in a longitudinal direction while the log is being cut by a rotary veneer lathe.

Another object of this invention is to provide backup rolls that operate independently of each other and are fed toward the center of the log being cut in a rotary veneer lathe at the same speed as the knife is fed into the log to resist the forces which tend to distort the log in a longitudinal direction.

These and other objects and advantages will become manifestly clear to those skilled in the art when taken in conjunction with the detailed specification and drawings wherein:

FIGURE l is a side elevation the present invention with internal details.

FIGURE 2 is a cross sectional view of the hydraulic rolls taken on line 2 2 of FIGURE l.

FIGURE 3 is a View similar to FIGURE 2 but illustrating the hydraulic backup rolls in an inoperative position.

FIGURE 4 is a detailed elevational view taken on line 4 4 of FIGURE 5.

FIGURE 5 is a cross sectional view of the hydraulic backup rolls taken on line 5-5 of FIGURE 4.

FIGURE 6 is a schematic illustration of the hydraulic system used with the present invention.

Referring now to the drawings, the hydraulic backup rolls of the present invention are generally indicated at 1 and consist of a pair of spaced-apart end stanchions 2 and 3 supported by a base member 34. Each of the stanchions 2 and 3 is provided with an arcuate recess 4 that accommodates or mounts a cylindrical cross member S in the form of a pipe. The cross member 8 is adequately supported by diagonal support arms 9 and 10 connected at its center point with a support member 11.

A conventional driving mechanism 5 is mounted at each end of the hydraulic rolls 1 and is provided with chuck spindles 6 that are rotatably mounted in the mechanism 5 and are movable inwardly and outwardly to chuck a log 7 therebetween. In this manner, the log 7 can be r0- tated by the driving mechanism 5 'by the chucks 6.

At each end of the cylindrical member 8 is mounted a support arm 12 of the backup rolls of parts broken away to show 1 12 by a pivot pin 13. In this manner, tne arm member 12 can move the hydraulic backup rolls 16 toward and away from the i the yoke 22 away from the log 7 by holding against the washer 24 on the rod 21. Nut 25 rigidly holds the washer 24 in position.

Intermediate the collars 20 is provided a cylinder 26 having a piston rod 27 connected to a piston 27 for moving the yoke 22 and roll 31 toward the log 7. The rod 27 is rigidly connected to the yoke 22 by a nut member 28. The cylinder 26 is rigidly mounted on the flange 19 by rods Z9 extending therethrough and through a top cover plate 30. As can be seen from FIGURES 4 and 5, there are two such hydraulic backup rolls mounted on the member S with both being identical with respect to each other. Accordingly, like numerals indicate like parts in both units.

Mounted at each end of the mechanism is a carriage cylinder 53 provided with a piston rod 63 having a piston 37 mounted thereon. Mounted adjacent the cylinder 35 is a switch 38 having a toggle arm 39 mounted thereon for a purpose to be hereinafter described.

A conventional lathe carriage having a knife thereon is generally indicated at 4f) and is provided with the usual knife means to sever the log in a manner so as to cut the log and provide a veneer 42 therefrom. Since the carriage illustrated forms no part of the present invention, suffice to say that it may be any conventional carriage that is capable of peeling a log to provide veneer 42.

In order `for the hydraulic backup rolls to function to maintain the log in a true cylinder, it is required that one end of the carriage cylinder be hydraulically connected to one end of the hydraulic backup roll cylinder 26. This is provided by lines 46 and 47 as shown in FlGURE 6. Also, lines 43 and 44 are connected to the lines 46 and 47 to ensure that adequate hydraulic fluid is supplied to each of the cyinders. Line 45 feeds hydraulic fluid from a pump S7 driven by a motor 56. Hydraulic fluid is supplied by a tank indicated at 58. A valve 59 is provided in the line 45 which can be opened and closed at will to provide make-up fluid that might leak in the system. Also, relief valves 52 and 5S are provided to ensure proper balance of the hydraulic fluid within the cylinders.

As can be seen from FIGURE 6, each of the cylinders on the rolls and carriage are provided with Openings or apertures 48, 49, 50 and Sl that open to the atmosphere to provide proper function of the piston within the cylinders.

In operation, the carriage is moved to the right as far as possible to receive a log 7 to be cut into veneer sheets. This is brought about in a conventional manner by withdrawing the spindles 6 and placing the log therebetween and then embedding the ends of the spindles 6 into the log with rotation being facilitated by the mechanism 5. The positions of the parts are indicated in FIGURE 3. As can be seen, the hydraulic backup rolls 16 are in an upright position and away from the log 7 being peeled. As the carriage 40 advances the knife into the log, a ribbon 42 is removed from the log and handled in a conventional manner. The carriage 40 will advance toward the log 7 by any conventional means such as a screw feed or a hydraulic feeding mechanism. When the carriage reaches a predetermined position, as when the log 7 is provided with a minimum diameter, the switch 38 will be actuated by the carriage engaging the toggle arm 39. This will actuate motor means 15 to eject the piston rod therefrom and move the arm 12 downwardly to a position shown in FIGURE 2. This will position the backup rolls 16 to offset any vertical or horizontal deflection of the log 7. As the carriage continues to advance into the log, the piston 37 Within the carriage cylinders 35 will eject hydraulic fluid through the lines 46 and `47 and into the cylinders 26 to displace the pistons 27' and move the rolls 31 outwardly. It should be noted that the ratio of displacement of the carriage cylinder and the roll cylinders is in a one to one ratio. That is, the piston 27 will be displaced exactly the same amount as the piston 37 so that the rolls 31 will not provide any force against the log core 7 unless the log 7 is deflected as a result of the force of feeding the carriage knife into the log. As the piston 27 is moved toward the log, the Spring 23 mounted upon the rod 21 will be compressed so as to hold the rolls upwardly away from the log 7. This ensures that no force is placed upon the log until such time as the log is deflected by the forces contemplated by the knife carriage. In this manner, a log 7 is always maintained in a true cylindrical form notwithstanding the external forces of the carriage and knife advancing thereinto no matter what the diameter of the log core 7 becomes.

When the log 7 becomes to a minimum diameter which cannot be peeled, the carriage 40 is reversed which moves the piston 37 in the opposite direction. The piston 27 then moves in the opposite direction under the influence of the springs 23 to remove the hydraulic fluid therefrom and replace it back into the carriage cylinder 35. Also, the arm 12 is pivoted around pivot pin 41 to be moved into a position as shown in FIGURE 3. The cycle is then repeated.

It is essential to the practice of the present invention that the hydraulic backup rolls do not add additional forces upon the log 7 as it is being peeled unless the log tends to deflect under the forces created by the car- :lage knife advancing into the log. Also, it is essential that the hydraulic backup rolls 16 be provided with rolls that will counteract the forces in equal and opposite directions. Accordingly, the radius of curvature of the recess 4 may be selected between wide limits to offset the resultant forces of the advancing knife into the log 7. The radius of curvature of the arcuate recess 4 will be selected according to the particular type of lathe operating conditions available since the position of the knife advancing into the log 7 will dictate the resultant forces that are created when the log becomes to a minimum diameter.

While the specific details of a preferred embodiment have been set forth above, it will be apparent that many changes and modifications may be made therein without departing from the spirit of the invention. It will therefore be understood that what has been described herein is intended to be illustrative only and is not intended to limit the scope of the invention.

What is claimed is:

1. An apparatus for stabilizing a log core in a rotating veneer lathe, said lathe being provided with a knife mounted in a carriage that is moved relative to the log at a controlled rate per revolution of the log comprising: spacedapart end stanchions; a cross support member; said cross support member being mounted between said end stanchions and movable toward and away from said log; at least one backup roll mounted on said cross support member engageable with said log only when the log tends to deflect; said backup roll comprising a hydraulic means associated therewith to move said backup roll toward and away from the center of said log; another hydraulic means responsive to the movement of said carriage; said hydraulic means being responsive to said another hydraulic means so that backup roll moves relative to said log at the same rate as said carriage moves relative to said log.

2. An apparatus in accordance with claim 1 wherein arcuate recesses are provided in each end stanchion to accommodate the cross support member.

3. An apparatus in accordance with claim 1 wherein said backup rolls comprise two members mounted on said cross support member with hydraulic means associated with each member together with two additional hydraulic means responsive to the movement of said carriage; said hydraulic means being responsive to said additional hydraulic means so that said members move relative to said log at the same rate as said carriage moves relative to said log.

4. An apparatus in accordance with claim 1 together with spring means mounted adjacent said backup roll to move said backup roll away from said log core when the hydraulic pressure thereof is removed.

5. An apparatus in accordance with claim 1 wherein said backup roll comprises a rotatable member mounted in a yoke rigidly secured to the end of a piston rod; said piston rod being connected to a piston within a cylindrical member; said cylindrical member being mounted 0n a support yoke rigidly attached to the cross support member; one end of said cylindrical member being hydraulically connected to said another hydraulic means.

6. An apparatus in yaccordance with claim 3 wherein said hydraulic means associated with said member is provided with apertures communicating with the atmosphere on the 4low pressure side of said piston therein.

7. A hydraulic backup roll in accordance with claim 5 together with two spring members mounted on each side of said piston rod for moving said piston rod in a reverse direction when said pressure is relieved.

References Cited UNITED STATES PATENTS 1,471,450 10/1923 Collier 144--209 2,766,786 10/1956 Molyneux 144-209 3,040,791 l6/ 1962 Fauchon 144-209 3,078,887 2/ 1963 Heth 144-209 DONALD R. SCHRAN, Primary Examiner. 

1. AN APPARATUS FOR STABILIZING A LOG CORE IN A ROTATING VENEER LATHE, SAID LATHE BEING PROVIDED WITH A KNIFE MOUNTED IN A CARRIAGE THAT IS MOVED RELATIVE TO THE LOG AT A CONTROLLED RATE PER REVOLUTION OF THE LOG COMPRISING: SPACEDAPART END STANCHIONS; A CROSS SUPPORT MEMBER; SAID CROSS SUPPORT MEMBER BEING MOUNTED BETWEEN SAID END STANCHIONS AND MOVABLE TOWARD AND AWAY FROM SAID LOG; AT LEAST ONE BACKUP ROLL MOUNTED ON SAID CROSS SUPPORT MEMBER ENGAGEABLE WITH SAID LOG ONLY WHEN THE LOG TENDS TO DEFLECT; SAID BACKUP ROLL COMPRISING A HYDRAULIC MEANS ASSOCIATED THEREWITH TO MOVE SAID BACKUP ROLL TOWARD AND AWAY FROM THE CENTER OF SAID LOG; ANOTHER HYDRAULIC MEANS RESPONSIVE TO THE MOVEMENT OF SAID CARRIAGE; AND HYDRAULIC MEANS BEING RESPONSIVE TO SAID ANOTHER HYDRAULIC MEANS SO THAT BACKUP ROLL MOVES RELATIVE TO SAID LOG AT THE SAME RATE AS SAID CARRIAGE MOVES RELATIVE TO SAID LOG. 